Liver transplantation: MR angiography with surgical validation

Thirty patients (mean age, 45 years) were evaluated with magnetic resonance (MR) angiography before liver transplantation to assess the accuracy of MR angiography. A series of breath-hold, two-dimensional images were acquired and subsequently processed to form three-dimensional projection angiograms. Graphic information on blood flow in the portal vein was acquired by using presaturation bolus tracking. Correlative duplex ultrasound (US) was performed in 28 patients, and surgical or autopsy correlation was available in all cases. MR angiography demonstrated patency of the portal vein in 26 (96%) of 27 patients, made possible the diagnosis of portal venous occlusion in three of three patients, depicted reversed portal flow in one patient, and provided clear delineation of the extent of varices and specific portosystemic collateral vessels. When duplex US was successful, there was full agreement with MR angiographic results in assessing portal vein patency and flow direction. All of the MR findings were corroborated at surgical exploration or autopsy. The authors conclude that MR angiography is very accurate in the portal system and is valuable in preoperative assessment for liver transplantation.     

Effects of acute aspartame and acute alcohol ingestion upon the cognitive performance of pilots

Anecdotal evidence has associated the artificial sweetener aspartame with a number of symptoms of central nervous system (CNS) dysfunction. There are, however, little scientific data concerning the effect of aspartame upon complex mental operations such as those necessary for flying an aircraft. Thirteen pilots were tested in a double-blind study using the SPARTANS cognitive test battery of aviation-relevant information-processing tasks. These tasks relate to perceptual-motor abilities, spatial abilities, working memory, attentional performance, risk taking, processing flexibility, planning and sequencing ability. Subjects were tested over five sessions consisting of pretest and posttest controls and three randomly ordered treatment sessions. The treatment conditions involved an aspartame dose of 50 mg/kg body weight, a placebo condition, and an ethyl alcohol (0.1% BAL) condition as the positive control. No detectable performance decrements were associated with the aspartame condition, although decrements in psychomotor and spatial abilities were detected in the ethanol condition. Results were found to be consistent with prior flight-simulator studies of alcohol, but do not appear to support the concerns expressed in anecdotal testimony regarding the deleterious effects of aspartame upon cognitive performance.     

Is three-dimensional computed tomography reconstruction justified before endovascular aortic aneurysm repair?

OBJECTIVES: The endovascular management of abdominal aortic aneurysm (AAA) relies on accurate preoperative imaging for proper patient selection and operative planning. Three-dimensional (3-D) computed tomography (CT) with reformatted images perpendicular to blood flow has gained popularity as a method of AAA assessment and image-based planning before endovascular aneurysm repair (EVAR). The current study was undertaken to determine the interobserver agreement of AAA measurements obtained with axial CT and reformatted 3-D CT and to compare the consistency of the 2 methods in selecting patients for EVAR. METHODS: Eight observers assessed the axial CT and reformatted 3-D CT scans for 5 patients with AAAs to determine whether the patients were candidates for EVAR. 3-D CT with multiplanar reformatted images was performed by Medical Media Systems (MMS). Each observer measured the length and diameter of the proximal neck, maximal AAA, aortic bifurcation, common iliac diameter, and aortic angulation. The proximal neck and common iliac arteries were also assessed for thrombus, calcification, and tortuosity. Agreement of the measurements on axial CT scans was compared with those on MMS CT scans by calculating the kappa statistic. Complete agreement was defined as kappa = 1.0. The limits of agreement between observers were also calculated. RESULTS: The cumulative interobserver agreement of MMS CT scans (kappa =.81) was greater than for axial CT scans (kappa =.59). The kappa value for each of the diameter measurements was greater with the MMS CT scans. In 79% of cases the observers' measurements were less than 2 mm from the mean with MMS CT, compared with 59% for axial CT. The kappa value for deciding whether a patient was an endograft candidate on the basis of aortic neck was greater with the MMS CT (0.92 vs 0.63). The limits of agreement between observers were also better with the MMS CT. CONCLUSIONS: The interobserver agreement in planning EVAR is significantly better with MMS CT compared with traditional axial CT. The routine use of MMS CT appears justified before EVAR to improve the accuracy and consistency of patient selection.     

Sodium retention in cirrhotic rats is associated with increased renal abundance of sodium transporter proteins

BACKGROUND: Liver cirrhosis with ascites is associated with a decrease in renal sodium excretion and therefore sodium retention. METHODS: In this paper, we utilize transporter-specific antibodies to address the hypothesis that dysregulation of one or more sodium transporters or channels is associated with sodium chloride (NaCl) retention in a rat model of cirrhosis induced by repeated exposure to carbon tetrachloride. Age-matched controls and cirrhotic rats were pair fed to ensure identical NaCl and water intake for 4 days prior to euthanasia for quantitative immunoblotting studies. RESULTS AND CONCLUSION: The rats manifested marked extracellular fluid volume expansion with massive ascites. Plasma aldosterone levels were markedly elevated. Analysis of immunoblots revealed marked increases in the abundances of both of the major aldosterone-sensitive apical transport proteins of the renal tubule, namely the thiazide-sensitive NaCl cotransporter NCC and the epithelial sodium channel alpha subunit (alpha-ENaC). These results are consistent with an important role for hyperaldosteronism in the pathogenesis of sodium retention and ascites formation in cirrhosis. In addition, we observed a large decrease in cortical NHE3 abundance (proximal tubule) and a large increase in NKCC2 abundance (thick ascending limb), potentially shifting premacula densa sodium absorption from proximal tubule to loop of Henle (which powers urinary concentration and dilution).     

Acute phosphate nephropathy following oral sodium phosphate bowel purgative: an underrecognized cause of chronic renal failure

The findings of diffuse tubular injury with abundant tubular calcium phosphate deposits on renal biopsy are referred to as nephrocalcinosis, a condition typically associated with hypercalcemia. During the period from 2000 to 2004, 31 cases of nephrocalcinosis were identified among the 7349 native renal biopsies processed at Columbia University. Among the 31 patients, 21 presented with acute renal failure (ARF), were normocalcemic, and had a history of recent colonoscopy preceded by bowel cleansing with oral sodium phosphate solution (OSPS) or Visicol. Because the precipitant was OSPS rather than hypercalcemia, these cases are best termed acute phosphate nephropathy. The cohort of 21 patients with APhN was predominantly female (81.0%) and white (81.0%), with a mean age of 64.0 yr. Sixteen of the 21 patients had a history of hypertension, 14 (87.5%) of whom were receiving an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. The mean baseline serum creatinine was 1.0 mg/dl, available within 4 mo of colonoscopy in 19 (90.5%) patients. Patients presented with ARF and a mean creatinine of 3.9 mg/dl at a median of 1 mo after colonoscopy. In a few patients, ARF was discovered within 3 d of colonoscopy, at which time hyperphosphatemia was documented. Patients had minimal proteinuria, normocalcemia, and bland urinary sediment. At follow-up (mean 16.7 mo), four patients had gone on to require permanent hemodialysis. The remaining 17 patients all have developed chronic renal insufficiency (mean serum creatinine, 2.4 mg/dl). Acute phosphate nephropathy is an underrecognized cause of acute and chronic renal failure. Potential etiologic factors include inadequate hydration (while receiving OSPS), increased patient age, a history of hypertension, and concurrent use of an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker.     

Incidents and complications during pediatric cardiac catheterization

BACKGROUND: Cardiac catheterization has revolutionized the management of pediatric cardiac disease. There has been little information on adverse events during these cases from an anesthesia viewpoint. The aim of this audit was to determine the incident rate during pediatric cardiac catheterization as contemporaneously reported by the anesthetist and to identify both the types of events and which procedures had the highest risk. METHODS: Since 1993, data have been collected prospectively on an audit form for every anesthetic given in our institution, and in-theatre events were recorded on this form. We have reviewed the data collected on pediatric cardiac catheterizations over a period of 9 years. RESULTS: A total of 4454 cardiac catheterizations were recorded. The overall incidence of events was 9.3%. Cardiac catheterization with occlusion of a patent ductus arteriosus (PDA) or a secundum atrial septal defect (ASD) had the lowest event rate at 4.2%. The figure for cardiac catheterization with other therapeutic interventions was 11.6 and 9.3% for solely diagnostic cardiac catheterization. The event rate in infants under the age of 1 year was 13.9% compared with 6.7% for those children over the age of 1 year. Of the 253 reports from cardiac catheterizations that could be analyzed further, there were 91 major complications including four deaths, 72 minor complications and 90 other incidents. CONCLUSIONS: Adverse events occur more commonly during cardiac catheterization than during pediatric anesthesia in general. Cases with highest risk are those in the under 1 year olds and those including a therapeutic intervention other than PDA or ASD occlusion.     

Alterations in the growth plate associated with growth modulation by sustained compression or distraction

Sustained mechanical load is known to modulate endochondral growth in the immature skeleton, but it is not known what causes this mechanical sensitivity. This study aimed to quantify alterations in parameters of growth plate performance associated with mechanically altered growth rate. Vertebral and proximal tibial growth plates of immature rats and cattle, and rabbit (proximal tibia only) were subjected to different magnitudes of sustained loading, which altered growth rates by up to 53%. The numbers of proliferative chondrocytes, their rate of proliferation, and the amount of chondrocytic enlargement occurring in the hypertrophic zone were quantified. It was found that reduced growth rate with compression and increased growth rate with distraction were associated with corresponding changes in the number of proliferative chondrocytes per unit width of growth plate, and in the final (maximum) chondrocytic height in the hypertrophic zone (overall correlation coefficients 0.38 and 0.56 respectively). According to multiple linear regression coefficients for these two variables (0.72 and 1.39 respectively), chondrocytic enlargement made a greater contribution to altered growth rates.     

Enlargement of growth plate chondrocytes modulated by sustained mechanical loading

BACKGROUND: Mechanical compression and distraction forces are known to modulate growth in vertebral growth plates, and they have been implicated in the progression of scoliosis. This study was performed to test the hypothesis that growth differences produced by sustained compression or distraction loading of vertebrae are associated with alterations in the amount of increase in the height of growth plate chondrocytes in the growth direction. METHODS: Compression or distraction force of nominally 60% of body weight was maintained for four weeks on a caudad vertebra of growing rats by an external apparatus attached, by means of transcutaneous pins, to the two vertebrae cephalad and caudad to it. Growth of the loaded and control vertebrae was measured radiographically. After four weeks, the animals were killed and histological sections of the loaded and control vertebrae were prepared to measure the height of the hypertrophic zone (average separation between zonal boundaries), the mean height of hypertrophic chondrocytes, and the amount of increase in cell height in the growth direction. RESULTS: Over the four weeks of the experiment, the growth rates of the compressed and distracted vertebrae averaged 52% and 113% of the control rates, respectively. The reduction in the growth rate of the compressed vertebrae was significant (p = 0.002). In the compressed vertebrae, the height of the hypertrophic zone, the mean chondrocyte height, and the amount of increase in cell height averaged 87%, 85%, and 78% of the control values, respectively, and all were significantly less than the corresponding control values. In the distracted vertebrae, these measurements did not differ significantly from the control values. The height of the hypertrophic zone and the mean chondrocyte height correlated with the growth rate (r (2) = 0.29 [p = 0.03] and r (2) = 0.23 [p = 0.06], respectively), when each variable was expressed as a proportion of the control value. The percentage changes in the measurements of the chondrocytic dimensions relative to the control values were smaller than the percentage changes in the growth rates, a finding that suggested that the rate of chondrocytic proliferation was also modulated by the mechanical loading. Conclusions: Mechanical loading of tail vertebrae in rats modulated their growth rate, which correlated with changes in the height of hypertrophic chondrocytes. The effects of compression were greater than those of distraction. Clinical Relevance: Information about the growth rate and chondrocytic response to mechanical loads in rat vertebrae undergoing mechanically modulated growth will be helpful in determining how human vertebral growth might respond to altered loading states during progression or treatment of scoliosis and other growth-related angular skeletal deformities.